Mine support grout packs

ABSTRACT

A grout pack is provided comprising a grout bag and a restraining envelope encircling the grout bag. The restraining envelope includes multiple elongate tension elements made of a multitude of fibres twisted, braided or woven to form confinement tension elements for operatively supporting the grout bag. The restraining envelope may include an inner mesh layer positioned on the inside of the elongate tension elements which may assume the form of containment rings encircling the grout bag at spaced positions up the height of the grout pack. Alternatively, or in addition, at least some elongate tension elements may extend in generally helical directions of opposite hand in the installed condition of the grout pack. The tension element may assume the form of a rope or a length of webbing. The ends of the rope or webbing may be joined in a manner providing for controlled slipping of overlapping ends thereof.

FIELD OF THE INVENTION

This invention relates to mine support grout packs of the type having agrout bag that, in use, is filled with a cementitious or other settablemix, typically, but not necessarily, including pulverised ore orbackfill of processed or barren mined material.

The term grout bag as used herein is intended to mean a generallypermeable bag that is used to contain slurry pumped into it underpressure and to retain the solids whilst allowing excess moisture topermeate through the grout bag wall that is typically made of a suitabletextile material such as a geotextile material.

The term grout pack as used herein is intended to mean a grout bag thatis used in combination with a restraining envelope encircling thegenerally upright walls of the grout bag, the restraining envelopeincluding either or both of a reinforcing mesh and a series of elongatetension elements typically in the form of confinement rings or bandsencircling the grout bag.

BACKGROUND TO THE INVENTION

Depending on the type and quality of rock being supported, the depth ofmining, the prevalent field stresses, seismicity, stoping width and anumber of other factors, stope support can utilise a vast range ofmaterials, configurations and systems, including, gum poles, timber andcomposite packs, steel props, unmined ore pillars, rock anchors andgranular (tailings) type supports.

Among the granular support media, cemented grout packs are increasinglybeing utilized as combination support products, consisting essentiallyof a support column formed by cured cemented backfill or a similar curedcementitious grout, contained within a geotextile bag and stiffenedagainst lateral deformation under axial load with an externalrestraining envelope of either or both of a reinforcing mesh and aseries of tension rings or bands encircling the grout bag, typicallyboth.

In a conventional configuration, a non-yielding type of grout packconsists of a grout bag surrounded by a restraining envelope includingsome form of mesh reinforcement and a plurality of confinement ringsencircling the mesh and bag. In the instance of yielding grout packs,the construction is similar except that the confinement rings or ringassemblies are able to yield under load thereby maintaining a measure ofrestraining force before their eventual failure. The mesh is typically areinforcement of wire or polymer netting and the confinement rings areusually made of steel wire.

Also, due to its relative rigidity, steel wire requires relativelycomplex production facilities for making the confinement rings. Also,the yielding characteristics of steel wire may not be appropriate asregards the yielding behaviour of the confinement rings.

OBJECT OF THE INVENTION

It is an object of this invention to provide a grout pack having analternative restraining envelope that is suitable for ease of productionand to provide for controlled collapse of an installed grout pack inuse.

SUMMARY OF THE INVENTION

In accordance with one aspect of this invention there is provided agrout pack comprising a grout bag and a restraining envelope encirclingthe grout bag, the grout bag having flexible side walls and two endsdefining, in use, a top, and a bottom and a cavity for receivingsettable granular material or grout, the grout bag further having aninlet for slurry to be introduced into the interior of the grout bag andwherein the flexible side walls are adapted to retain solids within thegrout bag and the grout bag has an axis in the general direction ofwhich a filled and set grout pack is adapted to yield, the grout packbeing characterised in that the restraining envelope includes multipleelongate tension elements each of which is made of a multitude of fibrestwisted, braided or woven or any combination thereof to form confinementtension elements for operatively supporting the grout bag.

Further features of the invention provide for the fibres to be polymerfibres including but not limited to one or more of polypropylene, nylon,polyesters, polyethylene especially high molecular weight polyethylene,and aromatic polyamides; for the restraining envelope to include aninner mesh layer positioned on the inside of the elongate tensionelements; for the elongate tension elements to assume the form ofcontainment rings encircling the grout bag at spaced positions up theheight of the grout pack in the installed condition; or, alternatively,for the elongate tension elements to extend in generally helicaldirections of opposite hand in the installed condition of the groutpack; and for the restraining envelope to include terminal rigidconfinement rings at each of its two ends, the rigid confinement ringsconveniently being of steel wire or similar relatively rigid material.

In one variation of the invention each tension element assumes the formof a rope that may be of a twisted construction or a braidedconstruction. In such variation the ends of a length of rope arepreferably spliced together to form an endless loop. The splice may beeither configured to be a non-slip type of splice or it may beconfigured to slip under predetermined loads in order to provide forcontrolled yielding of an installed grout pack.

In another variation of the invention each tension element assumes theform of a length of webbing. In such an instance the free ends of alength of webbing may be stitched together to form an endless loop.Alternatively, the free ends of a thing of webbing may be associatedwith a buckle that may be arranged to provide for yielding underpredetermined loads. In the event that the webbing is arranged in acriss-cross arrangement, the overlapping zones of the webbing can bestitched together.

The invention also provides a restraining envelope adapted to receive agrout bag in order to form a grout pack as defined above.

As a general rule, the grout packs defined above are preassembled at afactory level for transport, storage and conveyance to a site ofinstallation in a collapsed condition with the grout pack being readyfor installation and erection by securing the upper portion of theassembly against the stope hanging wall and filling the grout bag with asuitable settable material that is typically a cementitious materialintroduced in the form of a slurry.

In order that the above and other features of the invention may be morefully understood, various embodiments of the invention will now bedescribed with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:—

FIG. 1 is a schematic elevation of one embodiment of grout packaccording to the invention in an operative position between a hangingwall and a footwall;

FIG. 2 is a schematic plan view thereof; and,

FIGS. 3, 4, 5, 6, 7, 8 and 9 are each a schematic elevation of a second,third, fourth, fifth, sixth, seventh and eighth embodiment of grout packaccording to the invention.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

In the embodiment of the invention illustrated in FIGS. 1 and 2, a groutbag (1) has, in an operative inflated condition, generally cylindricalflexible side walls (2), and two end walls that form a top (3), and abottom (4) so as to define a cavity for receiving settable granularmaterial or grout as shown in the cut-away part of FIG. 1 and asindicated by numeral (5). A non-return inlet valve (6) is provided forthe introduction of granular material or grout in the form of slurrythat is to be introduced into the cavity of the grout bag, in the usualway.

The grout bag may be manufactured from a series of panels stitchedtogether or it may be made from a tubular textile material having endpanels secured thereto of the required shape defining the top andbottom.

The fabric from which the grout bag is manufactured may be any suitablefabric and, in particular, a geotextile is considered to be particularlysuitable, at least for the flexible side walls that are adapted toretain solids within the grout bag and allow water to permeate throughit as may be required. A similar result can be achieved in numerousdifferent ways and utilising numerous different designs.

In this particular embodiment of the invention a grout pack is formedutilising the grout bag described above together with a restrainingenvelope comprising both an inner peripheral supporting mesh (7)conforming generally to the outer shape of the grout bag in the opencondition and a series of operatively axially spaced circumferentialconfinement rings (8), the axis being indicated by line A-A in FIG. 1.

In keeping with this invention, each of the confinement rings (8) isformed from a synthetic polymer rope made of a multitude of polymerfibres twisted or braided together to form the rope. The free ends of asuitable cut length of rope are joined together by means of a spliceindicated by numeral (9) to form an endless loop. The splice can beconfigured in one of two different ways.

In a first way the splice is made to be non-slipping and a permanentconnection between the two ends. In such an event yielding is dependenton the stretch available in the rope and the rope will eventually breakat some point that will generally not be the splice.

In a second way the splice is configured such that when a predeterminedtension is exerted on the splice in consequence of the grout packyielding, the splice slips to allow the containment ring to increase insize whilst still retaining effective containment of the collapsinggrout pack. In such an event the confinement ring will eventually failonce the splice has slipped sufficiently to cause the splice toeffectively open.

In the embodiment of the invention illustrated in FIG. 1 the confinementrings are spaced equally up the height of the grout pack in theinstalled condition and are arranged to extend substantiallycircumferentially around the grout pack.

In the second embodiment of the invention that is illustrated in FIG. 3,the restraining envelope is devoid of any conventional mesh andcomprises multiple elongate tension elements in the form of helicallywound synthetic polymer ropes (10) extending in generally helicaldirections of opposite hand in the installed condition of the groutpack. In this embodiment of the invention the ropes extend at about 45°to the horizontal and are themselves interlaced to form a coarse meshwith diamond shaped apertures, as illustrated in FIG. 3. The ropes areattached at each end to a steel wire ring (11) of generally conventionalconfiguration at the top and bottom of the grout pack. The individualropes may include splice joints (12) made in either of the first andsecond ways described above.

In the embodiment of the invention illustrated in FIG. 4, the rope isreplaced by tension elements in the form of interlaced helically woundwebbing (15) and the steel wire rings are replaced by circumferentialrings (16) of webbing to which the ends of the helically wound webbingare secured by stitching (17) at the angle of 45°. Once more therestraining envelope is devoid of any conventional restraining mesh.

In the embodiment of the invention illustrated in FIG. 5, the elongatetension elements (18) are, once more, webbing. The webbing is wound inmore horizontal helices that make an angle of about 22.5° with thehorizontal or 67.5° with the direction of the axis of the grout pack.This flatter direction in which the webbing is wound translates intotension elements that carry a higher tensile load than in the instanceof the embodiment illustrated in FIG. 4 with the result that the groutpack will show a stiffer response under compressive load, in use.

In the embodiment of the invention illustrated in FIG. 6, therestraining envelope has both an inner peripheral supporting mesh (20)of generally conventional design conforming to the outer shape of thegrout bag in the open condition and a series of operatively axiallyspaced elongate tension elements in the form of spaced circumferentialconfinement rings (21) that in this instance are made of webbing. Theends of the webbing can be stitched together as indicated by numeral(22) and at least selected confinement rings can be provided withbuckles (23) that are configured to allow controlled slippage ofoverlapped end regions of the webbing to enable the circumferencethereof to increase and provide a yielding characteristic. The top andbottom rings (24) can conveniently be generally conventional steelrings, as described with reference to FIG. 3. The ends of both the meshand bag are secured to the steel rings.

In the embodiment of the invention illustrated in FIG. 7, thearrangement is the same as that described with reference to FIG. 6 apartfrom the fact that additional longitudinally extending tension elementsin the form of lengths of webbing (26) extend in a direction parallel tothe axis of the grout pack between the upper and lower steel rings (27).

In the embodiment of the invention illustrated in FIG. 8 the arrangementis substantially the same as that described reference to FIG. 4 exceptthat selected lengths of the helically wound webbing tension elements(30) are provided with buckles (31) that are configured to allowcontrolled slippage of overlapped end regions of the webbing to enablethe length thereof to increase and provide a yielding characteristicunder load. Also, FIG. 8 illustrates the fact that two layers of webbingcan be stitched together at selected points at which lengths of webbingcross each other, as indicated by numeral (32). In the embodiment of theinvention described with reference to FIG. 8, the ends of therestraining envelope are once more steel rings (33).

In the embodiment of the invention illustrated in FIG. 9, thearrangement is substantially the same apart from the fact that thewebbing tension elements (35) extend at a flatter angle to thehorizontal as in the case of the embodiment described with reference toFIG. 5.

Numerous variations may be made to the embodiments of the inventiondescribed above without departing from the scope hereof. In particular,it should be noted that the construction of the elongate tension memberscan be varied widely and is not limited to any of those described above.Also, wherever a steel ring is used, this may be a double steel ring tofacilitate attachment of any mesh that may be used and any elongatetension members to it. Also, any other type of fastening of the elongatetension members to each other or to an end confinement ring may beemployed.

Numerous other arrangements are possible within the scope of theinvention.

1. A grout pack comprising a grout bag and a restraining envelopeencircling the grout bag, the grout bag having flexible side walls andtwo ends defining, in use, a top, and a bottom and a cavity forreceiving settable granular material or grout, the grout bag furtherhaving an inlet for slurry to be introduced into the interior of thegrout bag and wherein the flexible side walls are adapted to retainsolids within the grout bag and the grout bag has an axis in the generaldirection of which a filled and set grout pack is adapted to yield,wherein the restraining envelope includes multiple elongate tensionelements each of which is made of a multitude of fibres twisted, braidedor woven or any combination thereof to form confinement tension elementsfor operatively supporting the grout bag.
 2. A grout pack as claimed inclaim 1 in which the fibres are polymer fibres selected from one or moreof polypropylene, nylon, polyesters, polyethylene and aromaticpolyamides.
 3. A grout pack as claimed in claim 1 in which therestraining envelope includes an inner mesh layer positioned on theinside of the elongate tension elements.
 4. A grout pack as claimed inclaim 1 in which at least some elongate tension elements assume the formof containment rings encircling the grout bag at spaced positions up theheight of the grout pack in the installed condition.
 5. A grout pack asclaimed in claim 1 in which at least some elongate tension elementsextend in generally helical directions of opposite hand in the installedcondition of the grout pack.
 6. A grout pack as claimed in claim 1 inwhich the restraining envelope includes terminal rigid confinement ringsat each of its two ends.
 7. A grout pack as claimed in claim 1 in whicha tension element assumes the form of a rope (8, 10).
 8. A grout pack asclaimed in claim 7 in which the ends of a length of rope are splicedtogether to form an endless loop.
 9. A grout pack as claimed in claim 8in which the splice is configured to be either a non-slip type of spliceor a splice configured to slip under predetermined loads in order toprovide for controlled yielding of an installed grout pack.
 10. A groutpack as claimed in claim 1 in which a tension element assumes the formof a length of webbing.
 11. A grout pack as claimed in claim 10 in whichthe free ends of a length of webbing are associated with a buckle thatis arranged to provide for yielding under predetermined loads.
 12. Agrout pack as claimed in claim 10 in which selected overlapping zones ofthe webbing are stitched together.
 13. A restraining envelope adapted toreceive a grout bag in order to form a grout pack as claimed in claim 1.